Instr is slightly faster than Like here (not that it matters much).

Debug.Assert False behaves identically to Stop. I use it if I am in
sort of a hurry: If there is not enough time to take care of all
possible error conditions (with adequate messages, logs, etc.) then I
try to ensure at least the success conditions for a program first. The
price is that the application is not foolproof yet.

Regards,
Bernd